This invention relates to an apparatus for preparing or constituting sizing compositions (hereinafter xe2x80x9csizexe2x80x9d) used in the manufacture of glass fibers on site just prior to their use. More specifically, an in-line mixing apparatus has been developed to mix the raw materials needed for a particular size with a carrier fluid, such as water, and deliver the newly constituted size to an applicator for application to the glass fibers on a substantially continuous basis.
In the manufacture of glass fibers, molten streams of fiberizable glass material are typically pulled through a bushing or ejected from a spinner and attenuated into fibers. Shortly after the fibers are attenuated, they are often coated with a size to retard interfilament abrasion and improve the handleability of the fibers, as well as to increase the compatibility of the fibers with the environment of their intended use. Typically, such sizes are aqueous solutions or dispersions containing film-forming polymeric materials, organosilane coupling agents, lubricants and various other processing aids, and are applied to the fibers by spraying or by passing the fibers across a pad or roll saturated with the size. However, for each glass end use application, a different size of unique formulation is often needed.
In the past, the production of size has typically been conducted through a batch process whereby the sizes are prepared off-line, stored and then used/applied as needed. Since the size needed for different glass fiber applications can be quite varied, the simultaneous running of different glass fiber production lines requires that a suitable quantity of various sizes be maintained on site. However, maintaining such an inventory requires substantial capital expense allocations. For example, facilities for the production and storage of size must be designed and constructed. The area must be large enough to house the raw materials, size formulating equipment and storage tanks for the batches of size. Additionally, the stored size must be maintained at proper temperatures to prevent deterioration.
Further, obvious problems can arise during glass fiber processing if an inadequate size inventory is maintained. Underestimating the quantity of size needed may result in costly events ranging from delays to a complete halt in glass fiber production. Moreover, since the sizes generally have a limited shelf life, overestimating the size requirements may lead to waste, as unused size may have to be discarded.
To alleviate the problems noted above, an in-line mixing apparatus has been developed for formulating the size continuously, as needed, just prior to its use. More specifically, an in-plant facility is provided for the substantially continuous manufacture of sizes immediately prior to their application to glass fibers, by adding the various components of the size together in a mixing apparatus and supplying the mixture to the sizing applicator. The components are chosen in accordance to the particular size required, and are injected into a stream of water or other carrier fluid flowing within the in-line mixing apparatus to constitute the size.
The mixing apparatus generally comprises at least two stages. The first stage providing a mixing device to mix together components used in preparing the size and disperse the mixture throughout the liquid carrier. The resulting mixture exits the first mixing device directly into a hydrolyzer, or second stage, where it resides for a sufficient time to allow the components to chemically react as desired. The mixture may then pass through additional mixing devices or stages if additional components are to be added to the mixture, or if greater residence time is needed to complete the desired chemical reactions between the components. Subsequently, the size may be piped directly to the size application device, or to a reservoir from which the size application device is fed.